154 Incidence of persistent lymphopenia in people with multiple sclerosis on dimethyl fumarate

Background Dimethyl fumarate (DMF) is a disease modifying therapy (DMT) used to manage Multiple Sclerosis (MS). The recently revised Summary of Product Characteristics (SPC) recommends increased monitoring or cessation this medication for persistent (> 6 months) lymphopenia, because an risk Progressive Multifocal Leukoencephalopathy. Awareness the frequency lymphopenia will guide clinical decisions regarding drug choice and safety monitoring. Methods Medical records 146 patients with MS, started on DMF between 2014-2020 who received > months treatment were reviewed identify incidence, duration, factors lymphopenia. Results Overall, 16 (11%) people MS taking experienced moderate (0.5-0.7x109/L 6m) 5 (3%) severe (<0.5 x 109/L 6m). Mean times 10.6 25.5 respec- tively. Increased age was predictor (B=0.071, p=0.004); sex previous DMT not. Conclusion Persistent – relatively common in DMF. More robust guidelines both risk/benefit continuing despite sequencing following are required.